Air springs are typically used in vehicular and industrial applications. In those applications, the air spring can serve, for example, to reduce road damage, to stabilize a vehicle, to reduce motion and/or vibration, to support a load, and/or to enable adjustments for driving conditions.
Air springs typically include two end members which are connected to respective ends of an air sleeve. The air sleeve can be composed of a fabric reinforced flexible bladder or sleeve. The air spring sleeve usually has opposed open ends which are connected to the end members by, for example, a clamp or swage ring to form a pressurized chamber within the sleeve. The flexible sleeve usually consists of inner and outer layers of a non-reinforced elastomeric material with a plurality of reinforcing schemes creating reinforcing layers sandwiched between these inner and outer layers or combinations thereof.
The inner layer, the reinforcing layer and the outer layer are typically made from a flexible material. The modulus of the flexible material of the air sleeve should be low enough to continuously flex as the air spring moves from extended to compressed positions without deteriorating to provide a durable air spring. To achieve that flexibility and durability, the art teaches a number of different sleeve constructions as well as sleeve compositions.
For example, the inner layer may be a particular elastomeric composition, while the outer layer may be of a different elastomeric composition. The use of different elastomeric compositions for the inner and outer layers, however, creates a stress discontinuity between the different layers of the air sleeve including the reinforcing layers. In addition, the use of a different rubber composition for each layer adds to the complexity of manufacturing the air sleeve.
U.S. Pat. No. 4,763,883 discloses an air spring bellows construction wherein the bellows is formed of elastomeric material and reinforced with embedded fiber cords. Successive layers of cord are wound in annular bands, either in the rolling lobe or in the chamber portion, in combination with helical windings to change angles of the cord material. That provides an air spring design that compromises the spring rate effect of a piston entering a chamber and increases the effective diameter of an air spring without substantially increasing its volume. In addition, U.S. Pat. No. 5,566,929 describes the use of three rubberized cord fabric layers to generate a longer service life at higher inner pressures and small roll-off radii in the rolling lobe.
Moreover, U.S. Patent Application Publication Nos. 2004/0248485 and 2005/0084638 are directed to particular plycoats that encompass reinforcement cords in an effort, inter alia, to obtain high resistance to deterioration of the bond with flexing of the air spring.